1. Field of the Invention
This invention relates to a probe for an electronic clinical thermometer, especially a structure of a temperature sensor including a thin-film thermistor, which is provided at a top end of the probe for measuring heat flux to predict a temperature of an object to be measured, especially a body temperature of a human body at any point from a surface to a deep part body of a human body.
2. Description of the Related Art
a usual method of measuring temperatures, including body temperatures, is performed by use of heat conduction, heat convection or heat radiation. The method requires a condition that the temperature sensor and the object to be measured should be in heat balance. Thereby, when the object to be measured has low heat conductivity, reaching in heat balance requires much hours, and shortening time for measuring causes lower measurement accuracy.
a surface temperature of the human body is lower than a deep body temperature thereof because of heat radiation from the surface of the human body. When the heat radiation could be perfectly prevented, the surface temperature will equal the deep body temperature. To overcome the above problems, a clinical thermometer, which can measure the deep body temperature by touching it on the surface of the human body, was developed.
Japanese Published Patent Application No. 2001-522466 proposes a method of measuring body temperatures of the human body by measuring heat flow. FIG. 5 is an illustrated cross-sectional view showing an inside of a top end of a probe, in which a temperature sensor disclosed in the above application is provided. According to the probe, a first temperature sensor 10 and a second temperature sensor 11 are formed on a flexible printed circuit board by photo-etching so as to provide a part of the flexible printed circuit board as a heat insulator 12 between the first temperature sensor 10 and the second temperature sensor 11. The flexible printed circuit board, on which the above sensors are formed, is rolled up or folded and inserted into the probe so as to touch the first temperature sensor 10 thermally to an inner wall of a metal case 13. The deep body temperature of the human body is calculated by heat conduction equation with measurement values of temperatures of the first temperature sensor 10 and the second temperature sensor 11 separated by the heat insulator 12 when a top end of the metal case 13 of the probe is touched to the surface of the human body. In other words, the deep body temperature of the human body is calculated with values of heat flow measured between the human body and the first temperature sensor and between the first temperature sensor and the second temperature sensor by the heat conduction equation. Measuring heat flow does not require waiting the sensors to reach in heat balance, so that the body temperature can be measured accurately and immediately.